Association between percentage of positive biopsy cores and risk of pelvic lymph node involvement in prostate cancer.

Abstract

205 Background: Commonly used tools for predicting the risk of pelvic lymph node involvement (LNI) in prostate cancer often do not incorporate information on the percentage of positive biopsy cores (PPB). To better inform the use of elective nodal irradiation in the definitive treatment of prostate cancer, we examined the association between PPB and risk of pathologic pelvic LNI in men with prostate cancer who underwent radical prostatectomy (RP). Methods: We identified 109,577 men from the National Cancer Database who were diagnosed in 2010-2015 with cN0M0 prostate cancer, had 6-24 cores sampled at biopsy, and underwent RP with pathologic nodal evaluation. Multivariable logistic regression was used to examine the association between PPB and the likelihood of having ≥1 positive pelvic lymph node, adjusting for other known clinicopathologic prognostic variables. Results: Overall, 4.0% (4,340) of the cohort was found to have pelvic LNI at the time of RP. Higher PPB was associated with an increased risk of pelvic LNI (adjusted odds ratio [AOR] 1.75 for 25.1-50.0% PPB, 2.63 for 50.1-75.0% PPB, and 4.49 for 75.1-100.0% PPB vs. ≤25.0% PPB, all P<0.001). Notably, men with Gleason 8 disease and ≤25.0% PPB only had a 3.6% risk of pelvic LNI, whereas men with Gleason 9-10 disease and 75.1-100.0% PPB had a 32.6% risk (Table). Other factors associated with the likelihood of pelvic LNI included a higher biopsy Gleason score (AOR 1.43 for Gleason 8 and 2.84 for Gleason 9-10 vs. Gleason 4+3, both P<0.001), more advanced clinical tumor stage (AOR 1.48 for cT2, 1.97 for cT3, and 3.87 for cT4 vs. cT1, all P<0.001), and a higher PSA (AOR 1.90 for 10.0-19.9 ng/mL, 2.40 for 20.0-39.9 ng/mL, and 2.60 for ≥40.0 ng/mL vs. <10.0 ng/mL, all P<0.001), but not more advanced age (AOR 0.98 for >62 years [median] vs. ≤62 years, P=0.59) or black vs. white race (AOR 0.99, P=0.92). Conclusions: There was a statistically significant and clinically relevant association between increasing PPB and a higher risk of pelvic LNI. As the ongoing RTOG 0924 randomized trial matures, clinicians should consider incorporating information on PPB in determining which patients with prostate cancer may benefit from receiving radiation therapy to the pelvic lymph nodes. [Table: see text]